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# Evidence for polaron conduction in nanostructured manganese ferrite

Gopalan, Veena E and Malini, KA and Saravanan, S and Kumar, Sakthi D and Yoshida, Yasuhiko and Anantharaman, MR (2008) Evidence for polaron conduction in nanostructured manganese ferrite. In: Journal of Physics D-Applied Physics, 41 (18). pp. 185005-1.

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## Abstract

Nanoparticles of manganese ferrite were prepared by the chemical co-precipitation technique. The dielectric parameters, namely, real and imaginary dielectric permittivity ($\varepsilon'$ and $\varepsilon"$), ac conductivity $(\sigma_{ac})$ and dielectric loss tangent $(tan \delta)$, were measured in the frequency range of 100 kHz–8 MHz at different temperatures. The variations of dielectric dispersion $(\varepsilon')$ and dielectric absorption $(\varepsilon")$ with frequency and temperature were also investigated. The variation of dielectric permittivity with frequency and temperature followed the Maxwell–Wagner model based on interfacial polarization in consonance with Koops phenomenological theory. The dielectric loss tangent and hence $\varepsilon"$ exhibited a relaxation at certain frequencies and at relatively higher temperatures. The dispersion of dielectric permittivity and roadening of the dielectric absorption suggest the possibility of a distribution of relaxation time and the existence of multiple equilibrium states in manganese ferrite. The activation energy estimated from the dielectric relaxation is found to be high and is characteristic of polaron conduction in the nanosized manganese ferrite. The ac conductivity followed a power law dependence $\sigma_{ac} = B\omega^n$ typical of charge transport assisted by a hopping or tunnelling process. The observed minimum in the temperature dependence of the frequency exponent n strongly suggests that tunnelling of the large polarons is the dominant transport process.

Item Type: Journal Article Publisher Copyright of this article belongs to Institute of Physics. Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy) 15 Oct 2008 11:19 19 Sep 2010 04:51 http://eprints.iisc.ernet.in/id/eprint/16136

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